Signature

This method contains the logic to be executed when removing this migration.

This method differs from down() in that the DB logic implemented here will
be enclosed within a DB transaction.
Child classes may implement this method instead of down() if the DB logic
needs to be within a transaction.

Note: Not all DBMS support transactions. And some DB queries cannot be put into a transaction. For some examples,
please refer to implicit commit.

Returns

Signature

This method contains the logic to be executed when applying this migration.

This method differs from up() in that the DB logic implemented here will
be enclosed within a DB transaction.
Child classes may implement this method instead of up() if the DB logic
needs to be within a transaction.

Note: Not all DBMS support transactions. And some DB queries cannot be put into a transaction. For some examples,
please refer to implicit commit.